Ok sorry about that! What you can do instead is pass the parameters arg to the run call of

FlowRunTask

like this:

with Flow("Parameter Getting") as flow:
    param = Parameter("task_param")

    flowRunTask = FlowRunTask(
        flow_name="next flow", project_name="Your Project",
    )

    flowRunTask(parameters={"task_param": param})

Is this supposed to work with

map

as well? Sorry for not explaining my exact usecase earlier. Below snippet demonstrates the exact usecase:

with Flow("Parameter Getting") as flow:
    param = Parameter("task_param")
    task1 = some_task()
    flow_names = another_task()

    FlowRunTask().map(flow_names, task_args={"parameters":{"task_param": param, "task1": task1}})

I tried applying your suggestion to map, but it throws same serialisation error at me. Also, there is output from another task that needs to be sent as parameter to next flow.

Ok so I couldn't get the flow run task to work out of the box with mapping, but subclassing it did the trick, you could try something like this:

import prefect
from prefect import Flow, task, Parameter
from prefect.tasks.prefect.flow_run import FlowRunTask

class MappedFlowRunTask(FlowRunTask):
    def run(self, ctx):
        self.flow_name = ctx["flow_name"]
        self.parameters = ctx["parameters"]
        super(MappedFlowRunTask, self).run()

@task
def get_flow_names(x):
    return [{"flow_name": "Parameter Printing", "parameters": {"task_param": x}}]

with Flow("Parameter Getting") as flow:
    param = Parameter("task_param", default="15")

    flow_names = get_flow_names(x=param)

    flowRunTask = MappedFlowRunTask(project_name="My Project")

    flowRunTask.map(flow_names)

(and should simplify the code a bit)